Vehicle engine systems such as those providing higher torque may utilize gasoline direct injection (GDI) to increase power delivery and engine performance. GDI fuel injectors in these vehicle engine systems demand fuel at higher pressure for direct injection to create enhanced atomization providing more efficient combustion. In one example, a GDI system can utilize an electrically driven lower pressure pump (also termed a lift pump) and a mechanically driven higher pressure pump (also termed a direct injection fuel pump) arranged respectively in series between the fuel tank and the fuel injectors along a fuel passage. In many GDI applications the higher pressure fuel pump may be used to increase the pressure of fuel delivered to the fuel injectors.
Vehicle engine systems may encounter fuel starvation issues when the lower pressure pump in the fuel tank run dry. One example approach to mitigate fuel starvation issues in an engine in a vehicle is shown by Zumbaugh et al. in U.S. Pat. No. 8,347,867. Therein, a fuel starvation detection module is employed to detect when an output of the lower pressure pump is lower than desired based on fuel fill level, air-fuel ratio, and fuel pressure of the lower pressure pump. In response to detecting a likelihood of fuel starvation, an amount of fuel supplied by the lower pressure pump to the engine is decreased for a duration.
The inventors herein have identified potential issues with the above approach to addressing fuel starvation. For example, fuel levels at different locations within a fuel tank can vary when the vehicle rounds corners and/or travels on inclines. Thus, the lower pressure pump, based on its location within the fuel tank, may experience fuel starvation and eventual degradation even if the amount of fuel supplied by the lift pump is decreased upon determining lower fuel fill. Further, in a vehicle fuel system including a plurality of lift pumps to provide higher power, merely decreasing the amount of fuel supplied by each of the plurality of lift pumps may not be sufficient to protect the lift pumps. To elaborate, as the fuel tank is drained of fuel due to continued operation of the plurality of lift pumps, at least a subset of the plurality of lift pumps may be situated such that their fuel pickup tubes are no longer submerged in fuel. As such, this subset of the plurality of lift pumps may degrade before fuel in the fuel tank is completely exhausted.
In one example, the issues described above may be addressed by a method for a fuel system in a vehicle, comprising supplying fuel from a common reservoir via each of a first lift pump and a second lift pump, and responsive to fuel fill in the common reservoir lower than a threshold, disabling one of the first lift pump and the second lift pump, and supplying fuel only via a remaining lift pump. In this way, pump degradation may be reduced.
For example, an engine in a vehicle may be coupled to a fuel system including two lift pumps: a first lift pump and a second lift pump, wherein each of the first lift pump and the second lift pump are situated within a common reservoir in a fuel tank. The first lift pump and the second lift pump may each supply fuel to a direct injection fuel pump and the direct injection fuel pump may, in turn, deliver fuel at a higher pressure to the engine. Fuel level in the common reservoir may be monitored by a fuel level sensor. As fuel fill in the common reservoir decreases to below a threshold, one of the first lift pump and the second lift pump may be deactivated. Specifically, one of the first lift pump and the second lift pump may be shut down. However, fuel from the common reservoir may continue to be pumped to the direct injection fuel pump via a remaining pump of the first lift pump and the second lift pump. Further, a controller may select which of the two lift pumps to deactivate based on whether the vehicle is traveling on an incline and/or rounding a turn.
In this way, dual lift pumps in a fuel system may be protected from degradation as a fuel tank is drained of fuel. By deactivating one of the two lift pumps based on fuel fill level and supplying fuel to the engine with the remaining lift pump, engine operation may be continued while reducing likelihood of degradation of one of the lift pumps. Further, in the event that the fuel runs out, the remaining lift pump may cease producing fuel pressure and the engine may stall disabling the remaining lift pump. Thus, degradation of the remaining lift pump may be averted as the engine is shut down. Further still, by selecting the lift pump to deactivate based on vehicle tilt and road gradients, the remaining active lift pump may be expected to draw fuel substantially continuously during its operation. Overall, durability and life of fuel system components may be extended.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.